In a tire including a land portion, movement performance on a dry road surface is improved by increasing a ground contact area of the land portion. Furthermore, sliding between the road surface and the land portion is reduced by suppressing local shear deformation of a rubber, which is generated at an end portion of the land portion, thereby improving the movement performance of the tire. Additionally, the actual ground contact area of the land portion is increased by removing water between a tread surface of the land portion and the road surface, thus improving the movement performance of the tire on a wet road surface during straight traveling.
Here, reduction in the ground pressure of the land portion at the end portion facilitates drainage of water on the tread surface into the groove to thereby remove more water. In association with the ground pressure reduction, conventionally, there has been a known pneumatic tire configured to reduce the ground pressure of the land portion at the end portion by forming the tread surface as an arc surface (see Patent Literature 1).
Incidentally, during cornering of the vehicle on the wet road surface, water tends to enter between the tread surface and the road surface and flow from the outer to the inner sides of the vehicle. In the prior-art pneumatic tire as disclosed in Patent Literature 1, water enters into an area around the center of the land portion, which might cause a risk of affecting both the ground performance and the movement performance of the land portion. In addition, during cornering of the vehicle, ground pressure of the land portion on the vehicle outer side rises, which might cause a risk of affecting the noise performance (quietness), and the movement performance of the tire on the dry road surface. Therefore, the prior-art pneumatic tire still has room for improvement from the viewpoint of ensuring high noise performance in addition to the movement performance both on the dry and wet road surfaces.